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Old Oct 16, 2006, 10:42 AM
Ship first, Improve often
L0stS0ul's Avatar
Virginia
Joined Apr 2005
5,008 Posts
agreed, and counter rotating ones as well
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Old Oct 16, 2006, 11:35 AM
Watts Rule, Glows Drool
dogon1013's Avatar
orlando, FL
Joined Mar 2003
3,197 Posts
Quote:
Originally Posted by Jagzilla
Well,mines 3/4 done. Just wanted to ask, does the elevator really need to be cut out, and then hinged? It seems fine just the way it is, not too much stiffness to it. Did you guys cut yours out and re-hinge?
J

Mine was rather stiff so I did cut it out and re-hinged it with the GWS hinges. I would suggest doing this if you are going to put the elevator servo in the boom. You don't want any stiffness if the servo horn is gonna be on the edge of the elevator, instead of the center.
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Old Oct 16, 2006, 12:05 PM
AMA 353531
rdeis's Avatar
United States, CO, Colorado Springs
Joined Aug 2003
6,553 Posts
Quote:
Originally Posted by Red 61
With respect to the CG issue -- in the REAL P-38, the pilot actually sits right on the CG.
Remember that full-scale CG's tend to be very forward for increased safety at the cost of efficiency.

Full scale CG's also move quite a bit in flight as fuel and ammo is consumed. Ours don't, so we can push them much further back for better flight performance.

Based on Red's experience, I's suggest that any belly-landers stay far away from 3 bladed props. Wheels-down only!

Also- varioprops and Grish props (if you can find them) are good choices for 3 blade counter-rotating P-38 props.
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Old Oct 16, 2006, 12:09 PM
Seeing the Farside.
Blaze.45's Avatar
Seattle WA, USA
Joined Aug 2005
4,285 Posts
Vario's would be excellent, but it'd be hard to make the scale size spinners work with it wouldn't it?

-Chris
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Old Oct 16, 2006, 01:39 PM
Registered User
kensp's Avatar
Darwin Australia
Joined May 2002
6,960 Posts
Quote:
Originally Posted by Jagzilla
Just to get this right in my head, even though the gws manual says 60mm back from where the middle (fuse) pod meets the wing (as shown on page 16 of manual), this is where the cog is, Kensp says it's around 93mm back from the same point. Thats a big change for sure. As I am getting ready to balance mine soon, I just want to make sure I'm reading this correctly, because between Ken, Rudedog and GWS, there's some big differences here!
jag
Jagzilla

My first flight was made with the CG at 1/3 of the distance between the Leading and Trailing Edges. This 1/3 chord distance was measured along the side of the pod but it could just as easily have been measured along the inner or the outer side of the booms as the GWS-38 wing has no sweepback. 1/3 chord is the conventional CG position for an model aeroplane with a wing in front and a tailplane behind.

Ken
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Old Oct 16, 2006, 03:43 PM
CAN WE MAKE IT FLY?????
rudedog's Avatar
Concord,N.C.
Joined Oct 2003
207 Posts
to clear up where my CG is it is 7mm infront of the wire groove on the underside of the plane...and she flys fine
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Old Oct 16, 2006, 04:22 PM
Pusher jets rule!
crxmanpat's Avatar
Mesa, AZ
Joined Jan 2006
17,212 Posts
I have been flying mine with the CG anywhere from 50-60mm. It does seem nose heavy, and I need to try to shift it back further to see if it handles any better. But it does fly.

Yesterday I flew it for the first time with the new Hacker A20-30Ms, and it still seems to be lacking in power. I may have to experiment with props. I'm at almost 1800' AGL, so that always has an effect on the prop selection. I used APC 9x4.7SF's yesterday, and I have a pair of 8x3.8's to try also. Moving my CG further back should help too.

It did fly nice and smooth still, and I was able to get some rolls and loops out of it, but I still need a little more speed. I have flown it both with TP1320's and TP2100's. The 2100's fit, but it adds weight. It seemed to fly just a little faster with the 1320's. I hate to add weight, but I may have to in order to get my CG further back.

Oh, and landing this thing is a dream! Nice and smooth on approach with about 1/4 throttle, and sets down nicely on the trike gear.

Painting is in progress, so I probably won't fly it again until finished.

@ Red 61, the pic I posted above of the battery location has a 2100 in it.

Pat
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Old Oct 16, 2006, 04:39 PM
Seeing the Farside.
Blaze.45's Avatar
Seattle WA, USA
Joined Aug 2005
4,285 Posts
Pat,

8x3.8's won't help your speed. Try 8x6HD's.

-Chris
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Old Oct 16, 2006, 04:39 PM
Registered User
kahloq's Avatar
Fort Collins, Colorado, USA
Joined Dec 2005
7,821 Posts
Quote:
Originally Posted by MERLIN V16
Is it not true that you can balance a plane anywhere by adding weight to the nose or tail (weather it be radio equip or clay)! Kensp has some repair weight on the rear of the tail boom I believe. Rudedog has a servo out in the tail boom.
with the differecces of Batteries,servos and motors the planes balance where they balance. And the both fly. I will admit the CG,s are a spread.
Let me make sure I understand what your saying......if you want to balance a plane at 60mm and the manual calls for say 80mm, yes you can balance yours at 60mm, but that doesnt mean it will fly right. You could balance it at 105mm if you wanted and it may fly(doubtful), but then it still will not perform as intended. Now, there are many cases where a manufacturers CG listing is not actually correct. So, if manual says 80 and you do 60 and it flies good, then maybe the manufacturer had a typo or some other mistake.

Yes...you can balance a plane by adding nose or tail weight. The purpose of that is to get the CG at a specific point...say 70mm from LE along fuse. Lets say for example you build a plane and manual calls for 80mm and you built it and it came out to 67mm without adding weight anywhere. In order to get the plane to balance at 80mm you would add weight (or move battery) to achieve the correct CG point.

Now, it is possible to get a plane to fly at CG points different from the recommended location(assuming the recommended one is optimal). So, manufacturers give a range....like 75mm to 85mm instead of saying 80mm with no give or take. In that range, the plane flies fine. Now...get quite a bit outside that and a plane will not handle as intended even if it does fly.

It concerns me(as probably several others) that there seems to be a huge range of CG that is being used and functions for this plane. Going from 60mm on one plane to 90mm on another is unheard of where the plane still flies ok. Some are saying that at 60mm, the plane is too nose heavy, so maybe going to 65-70mm as a starting point might be good...but at 90, thats a huge jump. This is a little baffling. I might put mine at 75mm just to split the difference.
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Old Oct 16, 2006, 04:43 PM
Registered User
kahloq's Avatar
Fort Collins, Colorado, USA
Joined Dec 2005
7,821 Posts
Well, after looking at the plane.....I am starting to actually dislike the darker color(mostly from a visual perspective of when its flying and being able to keep track of it). I may put it to ARMY green colors instead.
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Old Oct 16, 2006, 05:39 PM
Pusher jets rule!
crxmanpat's Avatar
Mesa, AZ
Joined Jan 2006
17,212 Posts
Quote:
Originally Posted by Blaze.45
Pat,

8x3.8's won't help your speed. Try 8x6HD's.

-Chris
Duh, what was I thinking. I have some APC 8X6SF's lying around. I'll try those next. They seem to work really well on my Esskay 400XT's, and the A20-30M's are similar.

Pat
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Old Oct 16, 2006, 05:45 PM
Pusher jets rule!
crxmanpat's Avatar
Mesa, AZ
Joined Jan 2006
17,212 Posts
Quote:
Originally Posted by kahloq
Lets say for example you build a plane and manual calls for 80mm and you built it and it came out to 67mm without adding weight anywhere. In order to get the plane to balance at 80mm you would add weight to the nose(or move battery forward) to acheive the correct CG point.
Actually, you have that backwards (I struggled with understanding CG too at first). If you balance at 67mm, and you want to move the CG back to 80mm, then you need to add TAIL weight. Because when you move the CG back, you are actually shifting more weight towards the front, and need to add weight to the rear to make it balance.

Quote:
Originally Posted by kahloq
This is a little baffling. I might put mine at 75mm just to split the difference.
Yes, it is baffling. I'm going to move mine back incrementally (5mm at a time), and fly it with the same motor/prop/battery combo and see what works best. Once I feel I have it dialed in good, I'll report back here and to GWS.

Pat
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Old Oct 16, 2006, 06:02 PM
Seeing the Farside.
Blaze.45's Avatar
Seattle WA, USA
Joined Aug 2005
4,285 Posts
I gotta say, from preliminary looks before paint or maiden... this is one beautiful recreation of the P-38.

You know a plane was done right when it has that striking look to it, and you find yourself staring into space at it sometimes. Or when you find yourself looking back at it when walking out of the room where it's sitting pretty.

My personal BIG Thank You to GWS for making this plane available to us at a great price.

-Chris
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Old Oct 16, 2006, 06:09 PM
Never Trade Luck for Skill
MERLIN V16's Avatar
United States, FL, North Port
Joined Jan 2005
12,903 Posts
?????????

Ok
Can someone explain which is the left and right boom? The GWS38 instructions show the seam on the outside and the channel cut for the CF rod on the out side.I see people Building it with the seam on the inside (the way i had it originally)The"circles" should be on the inside right? So why do the photos not show it that way! The Booms fit (kind of)both ways but i understand there is a built in thrust angle that makes them not interchangeable. I know it says R1-R2...L1-L2 on the inside half's,
but they are assembled now!
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Old Oct 16, 2006, 06:53 PM
Registered User
kensp's Avatar
Darwin Australia
Joined May 2002
6,960 Posts
Quote:
Originally Posted by MERLIN V16
Ok
Can someone explain which is the left and right boom? The GWS38 instructions show the seam on the outside and the channel cut for the CF rod on the out side.I see people Building it with the seam on the inside (the way i had it originally)The"circles" should be on the inside right? So why do the photos not show it that way! The Booms fit (kind of)both ways but i understand there is a built in thrust angle that makes them not interchangeable. I know it says R1-R2...L1-L2 on the inside half's,
but they are assembled now!
Actualy outthrust on a twin is desirable. If one motor cuts then the motor running is pullig against the turn. The clasic example of this is the JU-52.

Ken
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